Towed glider launching



plil 30, 1946 c. M. BoLs'rER TOWED GLIDER LAUNCHING Filed April 30, 19425 Sheets-Sheet l INVENTOR Calvin M Em'ler' BY A'ITOIZNEY Apfi 3m 1946.,

C. M. BOLSTER TOWED GLIDER LAUNCHING Filed Apil so, i942.

5 Sheets-Sheet 2 INVENTOR 3/ 32 TTDR EY 5 Sheets-Sheet 3 a v1.11 n SEr\` BY fffmff v AvroRNr-zY lll1lllllll.

l I Il Illlrlll C. M. BOL-STER TOWED GLIDER LAUNCHING Filed April so,1942 April@ s, w46.

pri 30, 1946.. QM. BoLsTER TOWED GLIDER LAUNCHING Filed April 3.o, 19425 Sheets-Sheet 5 EL 75 7/ /f TEF LM/ Y LNvENToR E. Elvin .L Hls WORNY rtow plane speed, while Patented Apr. 30, 1946 UNITED STATES PATENT-OFFICE y 2,399,196 'roWED GLIDER LAUNCHING calvin M. Bolsar, Unitedstates Navy Application April 30, 1942, Serial No. 441,187

19 Claims. (Cl. 244-63) (Granted under the act of March 3, Y1883, asamended April 30, 1928; 370 O. G. 757) The present invention deals withmethods and apparatus for launching gliders with the aid of a tow planein iiight.

The object is to make glider launching by meansV of tow planes simpler,easier and safer than it has been heretofore.

More specically, one of the objects is to provide means and methods forlaunching a glider bythe use of a tow plane travelling over the gliderto be launched, and picking up a bridle suspended between a pair ofpoles. The bridle is connected to a dual-sheave trolley mounted tooverhaul a doubled launching cable the loop end of which is passedthrough the trolley between the sheaves and is hooked to the glider, theloose ends being stretched outwardly and forwardly along the ground to apair of king posts fixed at some distance from the glider. As the bridleis picked up by the tow plane, it draws the trolley forward at theglider is given a gradually increasing acceleration until it reaches towplane speed at which time the trolley is automatically released from thebridle, while towing is taken over by a light tow line originallyattached to the bridle and paid out from a small reel in the glider aslong as the distance between the glider and plane increased.

Another object is to construct suitable automatic trolley release meansand provide precautionary safety measures to ensure the release of thetrolley from the bridle after the glider has reached tow plane speed.

Another object is to run the cables passing through thet rolley aroundposts in the ground located so as to modify the shape of the cablesbetween their xed ends and the trolley, in a manner to obtain a moreuniform acceleration for the glider.

Another object is to anchor the trolley at its starting position,connecting a bungee to it to give it its initial forward motion whenreleased,

y and providing means for releasing the trolley when the tow plane picksup the bridle, This device is used where it is necessary to reduce theinitial shock of starting the trolley and glider in motion.

The above and other objects will appear more fully from the followingdescription when considered in connection with the drawings, in which:

Fig. 1 shows the general ground layout of one preferred form of thearrangement wherein ve pairs of ground posts are used and illustrates`the four progressive positions of the apparatus vduring the launchingoperation.

Fig. 2 shows a glider in its initial set-up preto withstand the paratoryto launching, drawn on Va somewhat larger scale than Fig. 1.

Fig. 3 is a side view illustrating the relation of tow plane and gliderat the moment when the former is about to pick up the bridle.

Figs. 4, 5 and 6 show the relation of parts in progressive stages duringthe'launching operation.

Figs. 7 and 8 are plan and side views respectively, partly in section,of the trolley unit, with a special Yquick release device and a safetylink connected thereto.

Fig. 7a is a detail of a portion-of Fig. 7.

Fig. 9 shows the relation of parts of the trolley when the locking meansare released;

Figs. 10 and 11 are sections, thereof taken at the positions indicatedby the corresponding section lines in Fig. 7.

Figs. 12 and 13 illustrate a pelican hook quick release, that may beused in place of the jaw and release device shown in Figs. 7 and8.

Figs. 14 to 16 show details of one form of the vground posts,

Figs. 17 and 18 show diagrammatically a form of anchor plates which maybe used for the same purpose as the ground posts,

Figs. 19 and 20 are top and side views of a wrench adapted forinstalling the anchor plates.

Figs. 21 to 25 illustrate the trolley trigger arrangement for releasingthe trolley upon initial contact of the tow plane grapple hook with thebridle, and

Figs. 26 to 28 show the positive safety override release for thetrolley.

The problem involved in the present invention is to be able to pick up aglider and tow it easily out of a field of limited dimensions, and tofacilitate the launching of gliders from any field, regardless of itssize, by eliminating the necessity of carrying heavy launching andtowing equipment in the air or of providing a large bulk of launchingapparatus on the ground.

The common way of launching gliders, using a powered plane, has been totow the glider from the start on the ground. This requires a longrunway, careful handling and a strong tow-line comparatively largetowing forces encountered while the glider is drawn over the ground.

More recent methods include picking up the glider on the fly, butrequire an unusually long and heavy tow line a large part of which iswound on a large reel mounted in the glider, and a heavy brake system onthe reel to gradually apply the towing force to the glider through thetowline,

the free end of which is picked up at a distance from the glider by thetow plane.

The present methods require very little equipment, which is simple innature and very easily set up. Furthermore no equipment has to becarried in flight except a light comparatively short tow line and simpleattachments. Any plane equipped with a simple pick-up hook line may beused in these methods,

In general, Ythe glider to be launched is prepared by setting it out inthe ileld at Vsome distance to the rear and at equal distances from twospaced king posts. A launching cableA fastened at its ends to theseposts is hooked at its center to the glider, and the glider is draw-nback to take up the slack in the cable. A double-sheave trolley, madefor the purpose, is slipped over` the hooked loop of the cable bypassingthe loop between tne wheels, prior to hooking` the-cable to the glider.A looped bridle isattached to the trolley and its loop is hung over theglider so that it may be picked up by agrapple hooksuspended from thetow plane. When the bridle is picked up, it immediately draws thetrolley forward at tow plane speed butA the, glider gains speedgradually with an acceleration which depends on the characteristics ofthe layout of the cable and the ground posts, until the trolley reachesa point in line with the fastened ends of the cable. At

this'time obviously the glider has attained tow plane speed, because the'trolley has ceased to travel over the cables. Automatic release meansare provided to release the trolley from the bridle at this point, andvthe vtowing is taken over by a light tow line which had previously beenattached to the bridle and had paid out from the glider during itsaccelerating period. The trolley being free, the cablerbecomes loose anddrops off the hook on 'thegliden and both fall to the ground.Y Thebridle may also be dropped from the tow plane, after the lend of thelight tow line has been retrieved by Vit and fastened in the plane.

If desirable for any purpose, the releaserof the trolley could bedelayed until the glider attained a greater speed; but the trolley wouldhave Vto be released before the launching cable all paid out on itsreturn journey through the trolley.

YIn the preferred method, where the purpose is -to bring the glidermerely up. toy the tow plane speed, the trolley is released when itreaches a point Ain a direct line with the ground posts to which theVcable is fastened.

In a more specific form of Ythe method to be hereinafter disclosed, thevacceleration characteristics of the ground lay-out vmay be modified tosuit requirements. It may be shown that the acceleration of the gliderelfected by the present general method is variable and is a function ofthe angle. between the -two cables and of the distance of the gliderfrom the point midway between the ground posts'to which the cable ends 1lead. By placing :pairs of ground posts within the angle Awhich thetrolley makes with the king posts and passing `the line around the frontof these ground posts, the change in the angle may be Lmodified withrelation to the change in the distance above referred to, so as tomodify the acceleration characteristics within denite limits. By a.proper selection of the number and location of-theseadditional posts,an acceptable pattern may be designed with `a reasonably small numberofposts and comparatively small over-all space requirements, whichwillgive the glider .av substantially constant acceleration of 1.5 timesgravity, with a tow plane speed at about 90. M. P. H.

One specific form of apparatus which will carry out my method isillustarted in the drawings. The ground lay-out in Fig. l shows fourpairs of ground posts 2 to 5 inclusive in addition to the king posts Ito which the ends of the launching cable I8 are fastened. As may beseen, the points about which the two cablesy swing, change progressivelyfrom one pairof poststo4 the next, beginning with 5, as the trolleyproceeds on its journey. Four progressive steps in the launching areindicated in Fig.. 1, showing the corresponding relative positions ofthe plane, glider and launching cable Aat each step.

In Fig. 2 the glider 1 is shown in starting position .prepared forlaunching. The poles 8 are set upr behind the glider. The bridle 9 ishung over the poles and fastened to the trolley I0. The light tow lineI-I is attached to the bridle at I2. The side view of the glider in thisposition may be seen in Fig. 3which also shows the tow plane i3 flyingoverhead at'theinstant when its vhook I4 is about to pick up the bridle.The hook in this case is mounted on a rigid arm I5 pivoted in thefuselage of the plane to prevent fluttering of the hook under turbulentair conditions. I is a pick up line'to draw the bridle into the plane atthe vproper time. I1 is the tow line reel in the glider and I8 is thelaunching cable passed over a downwardly directed hook on the glider atI9. In the form of apparatus illustrated here, the trolley Yis held inananchor 22 on the ground by means of a triptrelease 'device which vistripped automatically at the instant the/bridle is picked up to releasethe ytrolleyfrom the anchor. The trolley besides being connected to thebridle is also hooked on to one end of the bungee 2|) stretched outinfront of it and anchored to the ground at 'its other end at 2l.. Whenthe trolley release `device .is tripped, the bungee initiates theforward `movement of the trolley 'so as to reduce the shock of itssudden acceleration to tow plane speed when theslack in the bridle istaken up. This .maynot be 'necessary in cases where this shock is notexcessive.

In Figs. 4 to 6 may be seen the relative position of the parts of theapparatus. in side .view in three consecutive steps indicated in planview in Fig. l.

A preferred form.. of trolley and its connections to the bridle areshow-n in detail in vFigs."l to 11. In this form, a safety link 23including .a breakable bar portion Mis inserted in the connectionbetween the trolley and the bridle. .If the release mechanism should`fail to function, this bar gives way before the subsequent overtaking ofthesplane by the glider, due to the Vfact that this bar portion isdesigned to withstand a maximum `stress between normal` towing force andtwice that amount. Normally, upon the slightest reversal of movement ofthe cables in thereverse direction through .thetrolley unit, as Vwouldoccur in launching as soon as the trolley passed the position in adirect line withfthe king posts, the pawls 25 swing outward againsttheir stops 26 as shown in Fig. 9, thus releasing the lock arms 2'I sothat they may be swung backward around their common pivot 29, inresponse to separation of the jaw. arms 3 I, As a result of the 'pull onthe'coupling member 34 the jaws 32 then open against the tension springsV33 which normally move'them to closed position, vand the trolley andcables fall away to the ground.

In order to makethe coupling, in preparation for ythe next launching'allthat isjnecessaryto do is to insert the coupling 'member inthe *jawswhile swinging them open manually by means oi the studs extendingthrough accurate slots 39 in the cover 40. Upon releasing them they willautomatically close due to the tension of springs 33. The jaw arms arethen locked byfmanually swinging the lock arms outward against theirstops 36 with the aid of the studs 38. In doing this the pawl units 25will be swung under the ends of the lockarms because of the tension ofsprings3l and will thus set the lock ready for operation as describedabove. 4| and 42 are spacers and 43 are rubbing strips to prevent thecables Yfrom fouling. Nuts 44 are for the removal of the top cover foraccess and removal of the ratchet pawls and levers, While the nuts 45Yon the bottom are for removal of bottom plate 46 for access to andremoval of the sheaves or-wheels 41.

Figs. 12 and 13 illustrate another form of trolley having a pelic-anhook coupling with a quick release upon reversal of the movement of thecables. The resulting reverse rotation of the sheaves trip the pawl andratchet locking means to Vrelease the pelican hook 4B whichautomatically unhooks the link 49Aconnected to the bridle.

One form of ground posts to be used for deflecting the launching c-ablesbetween the trolley and the king posts to modify the accelerationcharacteristics is shown in detail in Figs. 14 to 16. Another form ofdevice which may be used for the same purpose is disclosed in Figs. 17and 18. In the rst form, the main parts ofthe unit are the two Tsectioned stake portions 50 and 5l driven into the ground back to back,the shorter portion being backed -up by the longer one. The cablereceiving portion 52 is biuted to the top of the web of the short stakeas shown, at 53, on a level with the ground. A lining 52 may be usedunderthe piece 52 and between the stake portions as` shown.

The vplate form shown in Figs. 17 and 18 is installed by the aid of aWrench shown in Figs.

19 and 20. The plate 54 with the cable receiving portion 55 weldedthereon is placed in the desired location and the flat headed screws 56are driven through the openings '53 in the corners of the plate into theground by means of the wrench tool 59 and its studs B0 which fit intothe bores 6| in the screw heads. The wrench is offset a suitable amountB for hand clearance and its arms may be of any convenient length A.

'I'he"details of the trolley anchor and release means may be seen inFigs. 21 to 23. The bridle which is attached to the trolley by the linkmeans 62 as shown, is hung over -a pair of rockable levers 63 pivoted atthe top of the poles 8, formed so as to draw the link means up uponswinging in response to the initial contact of the bridle with Athe pickup hook. The upward motion of the link 52 trips the lock means 64 andreleases the trolley from its anchor 65. The bungee 20 being stretchedforward and hooked to the trolley'at iBS, starts the trolley on its way,to reduce the shock of its beingY picked up by the-fastmoving plane whenthe bridle is fully stretched out forward thereby. Hook 56 is made sothe bungee will readily drop olf after having performed its duty. Theanchor plate 65 has guide rails 61 on which the trolley sets when placedin starting position with its rear edge under the clips 68.

A positive trolley release device such as shown in Figs. 26 to 28 may beprovided to ensure its release'as a safety precaution in case the otherre- 'lease devices should fail to work. The pawl units 25`ln thisdevice:are extendedto form arms 69 which may be positively kicked to therelease position by striker members 10 slidably mounted in the cover 4Uand having yokes 1| at their other yends straddling the cables I8. Onthe cables near their glider ends are large swaged fittings l5 whichwill not pass through the yokes. These ttings are small enough to passthrough the trolley and when travelling therethroughin the normaloperating direction they will merely push the yokes out of their waywhen coming out of *the trolley, the yokes being pivotally mounted onrection by the shoulder 13. The spring 'Hl returns them to operatingposition if they should be swung in the other direction during normaloperation;

To obtain a constant acceleration of the glider from a substantiallyconstant speed of the plane, in the method of launching hereindisclosed, it may be shown analytically that for any predeterminedoperating speed of the plane the launching cables would have to bedeflected by a curved convex surface inwardly and forwardly, having aparticular curvature depending on the distance between the startingpoint of the glider and the king posts and the distance between the kingposts. This curvature may be reasonably approach'ed by the use of only afew pairs of posts such as the ground postsV herein described in placeof the curved surface by placing them in selected positions, chosen soas to maintain the rate of acceleration between certain narrow limits.

In practice of course the plane speed would decrease a certain amount ifthe transfer of energy from the plane to the glider were not compensatedfor by increasing the power supplied to th'e plane by its propellers.This reduction however will either be negligible if the comparativeweight and drag characteristics of the glider are negligible taking intoaccount the acceleration characteristics of the apparatus used, or itmay be satisfactorily compensated for,y if there is a reserve of poweravailable, by adjusting the power controls to meet the requirements ofadditional energy transferred to the glider vto overcome its inertiaduring the acceleration and its increasing drag as its speed is builtup. I

From the foregoing description and the disclosure in the drawings whichare merely illustrative, it is evident that various modifications andchanges in the design of the apparatus and methods may be resorted towithout departing from the spirit of the basic invention or the scopeofy the appended claims:

The invention described herein, if patented,

may be manufactured and used by or for the Government for governmentalpurposes without the payment to me of any royalty thereon.

I claim:

1. In a launching apparatus for a glider to be towed by a plane inflight, a, launching hook on the glider, two king posts fixed in theground at substanitally equal distances in front and to each side of theglider, a dual-sheave trolley, a cable stretched between said posts andextending to the glider, said cable being doubled at this point, theresulting loop passed between the sheaves of said dual-sheave trolleyand attached to said launching hook on the glider,l a pole set up oneach side hung over thev top .of the poles, means for automaticallyreleasing ithe trolley and cable from` vsaidbridle and:glider-1respectivelywhen'said:trolley is drawn forward beyond atpositionnpllne with` the kingY posts.

f2. In alaunching apparatusorra gilden-a dualsheave trolley, alaunchingcableglaid Yout `onfthe .matically releasingztheptrolley; from.the Aplane and the cable from the `glider-atten `the glider :hasreached the planes speed.

3. Apparatus-for launching a, glider ,by means of towplanes .in flightcomprising: :alaunching hook under rthe glider nose; a dual-sheavetrolley, a launching cable stretched out ina Vshape having its endsfixed to the ground and its vertex passed through the `trolley andhookedto :the launching hook, `a bridle attached to theftrolley and having aloop, apair ofpoles at'thesides .of the glider over which'the loop ofathe rbridle is stretched, means on the tow planev for .picking up thebridle by its loop-as the planeviiies inV a steady level course overthe-glider, means for releasing the trolley fromthe bridlein response tothe ,rotation of `the sheaves in reverse'direction after the trolley.has passed the vertical plane through the points where the -cable isiixed to the ground,'the cable being then Yfree to drop oiY the gliderhook.

4. Means for launching towedgliders including towing means, a cablesystem for imparting a gradually increasing Vspeed to theglider from asubstantially constantspeed of the .tow-

ing means, means for releasingthe cable system from the gliderand-towing means after the glider reachesthe speed ofthe Vtowing means.

5. Apparatus for launchingtowed gliders including a tow plane, a cablesystemfattached to the glider on the ground'and Ahavnig agraduallydecreasing mechanical 4advantage when in use, means on the plane forhooking'onv to this Vsystem while flying over it toY put it inoperation,i

means for releasing said cable systemfrom-the plane and glider when thelatter attains the speed of the vformer.

6. Apparatus as .brought out .in claim 5 .in

which a light weight tow line-fisi'mounted -on a reel in the glider,means for picking up onek end of this tow line bythe `plane when-'ithooks on to the cable system, means for fastening the tow line in theplane and glidertccontinue the towing after the v cablesystem isreleased.

7. In an apparatus for launching towed gliders, a trolleyhavingftwosheaves,acage for mounting the sheaves tangentially adjacentto each other, means attached to saidcageforconnection to a bridle,means forlocking this connection means, release means for .sa-id lockingmeans responsive to rotation of the sheaves in one direction only.

8. A trolley including a sheave, acage "for said sheave, means forreleasabl-y :connecting said cage to a line, locking means for saidconnecting means, and release means responsivce r`to one direction ofrotation of the sheave to release the locking means thus causinggtheconnection 'to break.

9. In a cable system for launching gliders and the like, a cable, atrolley including a sheave, Aa cage in which the sheave is mounted, alinev for pulling the trolley over said cableimeansia releasableconnection: between.` thev .cage :and the line,` locking means for saidconnection, `,means responsiveto a reversal fof rotation ofthe sheavefor releasing said locking means and allowing the connectionto bebroken-by the applied force.

10. In-afgliderlaunching apparatus, a hook at the'ancse of the glider, acable streached out in y.theform of a AV 'on the ground and having. its

`endsfxed, a trolley havingahousing with openingsatthe front and rear,two sheaves mounted `tangentiallyto eachother in ysaid housing so thattheirlineof'tangency passes through the openings, the vertexof theV-shaped cableV .being -passed .through these openings from front torear 4ofsaid housingfbetween the sheaves and looped voverthe hook vat`the: nose of the glider just back of the/trolley, a connectionreleasably connected tothe trolley housing, means ymounted in thetrolley housing for locking said connection and means for releasingvsaidlocking means respon- Vsive-.to movement of the cableorward through the'trolley housing. l1l. In a glider launching apparatus, a hoo at Ythenose-of theglider, acable stretched out `inztheforni of 1a V on theground and having its ends fixed, atrolley having a housing withopenings at the frontand rear, two sheaves mounted just back of thetrolley, anchor means on .the

ground for the trolley housing, a vvertically operated key for lockingVsaid housing to'the anchor when in its lower position, a hook under thefront of said husing, a stretched out `bungee having a loop at one endpassed over said hook under said housing and being anchored tol theground in front of the glider, a connection releasably connected to thetrolley housing, a link passed under'said key pivotally fastened back ofittov said connection so as to release the trolley from'its anchor whenthe link is drawn upward and the key is pulled up, means mounted in the-trolley' housing for locking said bridle connection, and means forreleasing said locking means `responsive Ato movement of the cableforward through ,the trolley housing.

12;.In a glider launching apparatus,l a hook at the nose of jthe glider,a cable stretched out in the form of V on thev ground and Ahaving its`ends fixed, a trolley having a housing with openings atithe front andrear, two sheaves mounted tangentiallyto each other in said housing sothat their :line of tangency passes through the openings, the vertex ofthe V-shaped cable being passed vthrough these openings 'from front torear Y of saidhousing between the sheaves and looped -over the hook atthe Vnose of the glider just back of vthe trolley, anchor means on theground for the trolley housing, a .vertically-operated key for lockingsaidhousing to the anchor-when in'its lower position, a hook under thefrontof said housing, aistretched out -bungee havinga loop at one-endpassed over said hook .under said housing and being anchored to theground in front of the gli'dena bridle, a connection releasablycon.-

'nectedto 'the 'trolleyihousing alink between said bridlefand said-connectionfsaid llink being passed .under said key and vpivotallyfastened back .of it to said'connectionso aste release the trolley fromits anchor'when :the link isidra'wn upward by; raisthe bridle end:thereof ,thus 'pulling' .up-the ikeynut oft -its lock position, means;mounted" in the trolley housing for locking said bridle connection, andmeans for releasing said locking means responsive to movement of thecable forward through the trolley housing.

13. In a glider launching apparatus, a launching cable stretched out inthe form of a V xed to the ground at its ends, a glider attached at thevertex, a double sheave trolley mounted over the two side portions ofthe cable at the vertex to draw the two sides of the V together byrolling the sheaves over the doubled cable beginning at the vertex,pairs of ground posts for deecting 'ie two sides of the V inwardlyatvintervals, symmetrically along lines forming angles at the posts, s-oas to approach a constant acceleration of the glider at any particularspeed of rolling of the trolley over the doubled cable.

14. In a glider launching apparatus, a hook at the nose of the glider, acable stretched out in the form of V on the ground and having its endsfixed, a trolley having a housing with openings at the front and rear,tw-o sheaves mounted tangentially to each other in said housing so thattheir line of tangency passes through the openings, the vertex of theV-shaped cable being passed through these openings from front to rear ofsaid housing between the sheaves and looped over the hook at the nose ofthe glider just back of the trolley, va connection releasably connectedto the trolley housing, means mounted in the trolley housing for lockingsaid connection, means for releasing said locking means responsive tomovement of the cable forw-ard through the trolley housing and, safetymeans forl positively operating said release means including swagedportions on the cable A small enough to pass through the trolley sheaveswithout binding, a bar slidably mounted in the rear portion of thetrolley housing parallel to the cable and having a forked memberpivotally mounted thereon and resiliently held against a shoulder on thebar in such a position as to straddle the cable, and so that it will bepushed out of the way by the swaged portions against the tension of thespring when the cable moves back through the trolley but when the cablemovement is reversed these portions will not pass the forked member butwill push the bar forward in the housing, means in the housing operatedby this forward movement of the bar to positively release saidconnection locking means.

15. In a glider launching apparatus, a ground post used for deectingcables stretched out along the ground, consisting of a pair ofT-secti'oned bars adapted to be driven vertically into the ground withthe sections corresponding to the top of the T adjacent each other, ahead piece fastened to the top of the web of one bar and having a groovefor the cable.

16. In a glider launching apparatus, a ground post used for deectingcables stretched yout along the ground, consisting of a pair ofT-sectioned bars adapted to be driven vertically into the ground withthe sections corresponding to the top of the T adjacent each other, ahead piece fastened to the top of the web of one bar and having a groovefor the cable, the other bar beine longer than the rst.

17. In a glider launching apparatus, a ground post used for deilectingcables stretched out along the ground, consisting of a pair ofT-sectioned bars adapted to be driven vertically into the ground withthe sections corresponding to the top of the T adjacent each other, ahead piece fastened to the top of the web of one bar and having a groovefor the cable, the said bar having the lower portion of its adjacentsection widened for better anchorage.

18.. In a glider launching apparatus, a ground post used for deflectingcables stretched out along the ground, consisting of a pair ofT-sectioned bars adapted to be driven vertically into the ground withthe sections corresponding to the top of the T adjacent each other, ahead piece fastened to the top of the web of one bar and having a groovefor the cable, the said -bar having the lower portion of its adjacentsection widened for better anchorage, said head piece having fairedsegmental surfaces above and below the groove to prevent fouling of thecable as it is swung out of the groove in the operation of the launchingapparatus.

19. In a towed glider launching apparatus, a dual-sheave trolley, apelican hook linked to said trolley, a lever pivotally mounted on thetrolley having an opening that ts over the end of said hook when thelatter is in closed position, resilient means fastened to said trolleyto urge said lever into hook-engaging position, means operated inresponse to rotation of the sheaves in one direction to rock the leveragainst the lpressure of said resilient means to release the hook.'

CALVIN M. BOLSTER.

